Elements of Non-Fiction in Fiction

I am a firm believer that non-fiction ideals can always be found in any piece of literature, or even art for that matter.  At the most basic level, human beings are non-fiction.  Yes, we all tell lies and our thoughts often live in a fictitious world, but our existence according to our human knowledge is a reality and a truth. 

Truth is relative according to the self.  Something that may be completely true and concrete to me, such as my belief in humanity in all people, would be completely fiction to another who has maybe encountered someone who is a testament of a savage.  Going further, relativity is relative.  Say that something is fact relative to me.  The fact that that fact is fact relative to me may or may not be fact relative to someone else.  This continues infinitely.

Take my song of the day, Young and Beautiful by Lana Del Rey, for example.  It is a conversational piece where Del Rey sings to her lover talking about their future relationship with the main lyric of the song being, "Will you still love me when I'm no longer young and beautiful?" These words can be considered a form of poetry or she could be talking to a fictitious, imagined person. Nonetheless, this line in non-fiction relative to its setting.  They can still be non-fiction if they are coming from one fabricated character to another.

Young and Beautiful by Lana Del Rey